Programming ADF4153

We are trying to program a minicircuit device (DSN 2036 +119), which has as its heart the ADF4153 PLL synthesizer, but the programming is not occurring. At least the locking is not happening nor the Muxout set as Dvdd is going to high.

We are following this algorithm (based on the ADF4153 datasheet and using a SPI module from an ATTiny uC)):

1. Write all zeros to the noise and spur register (R3).

- LE low

- Load 0x000003

- LE high

2. Write again to the noise and spur register, this time selecting which noise and spur mode is required.

- LE low

- Load S (table bellow)

- LE high

3. Enable the counter reset in the control register by writing a 1 to DB2; also select the required settings in the control register.

- LE low

- Load C (with this modification:0x000546)

- LE high

4. Load the R divider register (with load control DB23 set to 0).

- LE low

- Load R

- LE high

5. Load the N divider register.

- LE low

- Load N

- LE high

6. Disable the counter reset by writing a 0 to DB2 in the control register.

The reference frequency is 10 MHz and I am trying to lock 1653.42 MHz.

About the Resync bit, it was a mistake when I wrote it before. It is actually set to 1.

Let me tell you that I programmed the uC to send the data into the ADF4153 after 5 seconds and I noticed that the Muxout PIN, which should show me 5 V after programming, changes from 0 V to 0.004 V exactly 5 seconds after I power up the circuits.

Another interesting thing is that even if I don't try to program anything, a carrier with good power (-1 dBm) appers at 2.11 GHz. This happen when I power up the VCO after the PLL.

I tried with other code. This time simulating the SPI by GPIO and I got the dropping and increasing of current when I do the procedure you suggested (powerdown one).

In any case trying to program to the desired frequency, the following happens:

1. I power all the devices up;

2. Two carrier frequencies appear on the spectrum analyzer; and

3. After the 5 seconds I put for starting the programming the plan frequency on the spectrum changes and then I have 3 carriers with 700, 1550 and 2000 MHz approximately.

When the Muxout pin is set as high (using the control register) I can check 2.5 V on it after programming. But when I set to Lock Detection it stays on zero in the end of the previous steps I just commented.

I see that the device is being programmed, but what could be wrong now!?

When you power up the VCO, on its output you will see the frequency which is related to the tuning voltage on its tuning port. For ADF4153, after power up and before the part is not programmed, the charge pump is in three-state, which means there is no charge pump current going out of the pin. As a result, the voltage on the output of the loop filter should be 0 and the VCO should go to the minimum or maximum frequency that it can cover - minimum if the VCO has postitive polarity (which means the frequency increases when the tuning voltage increases), maximum in case it has the negative polarity (frequency decreases when tuning voltage increases). But keep in mind that in case when an active loop filter with inverting topology is used, it will change the behaviour of the VCO so it will behave as it was of opposite polarity.

You will see as well harmonics on the VCO outputs - so you can observe more than one tone on the spectrum analyzer (first is the carrier and it should be the highest peak as it has maximum power, and them its harmonics - each of them should have lower power and should be at frequency that is multiplication of the carrier frequency - by 2, 3, 4 etc.) The number of the harmonics will depend on the span setting on your spectrum analyzer.

You mentioned that after power up, the VCO goes to frequency 2.11 GHz, However, later you mentioned that after programming the part you see three spikes: at 700MHz, around 1550 MHz and 2 GHz. This information makes me to ask you more details of the VCO you use and about the loop filter.

1. What VCO do you use?

2. What frequency range does the VCO cover?

3. Could you measure the tuning voltage on the VCO tuning port and the frequency on VCO output after power up?

4. Does the VCO have a positive or negative polarity?

5. Do you use a passive loop filter or an active loop filter (if so, which topology)?

Further, you have noticed that Muxout pin does not go up as it should, but you expect 5 V there - it is not possible, as the AVDD and DVDD are within range 2.7 V to 3.3 V and when Muxout is high the voltage should be the same as DVDD. Similarly, the level of the signal provided to the programming interface is limited - it should be at the same value as AVDD and DVDD. So one more questoin:

6. What is the level of the signal from the microcontroller to the CLK, DATA an LE pins? Do you comply with the limits in the datasheet or do you drive these input with 5 V?

The ADF4153 is installed inside a Mini Circuit Device called DSN 2036 +119, so I dont have access to the information about the VCO. But the MC Device goes from 925 MHZ to 2036 MHZ.

However let me tell you what I noticed from my trials.

First of all I have noted that the INITIALIZATION SEQUENCE given by the ADF4153 datasheet page 18 differs from what I have seem the people using and also from what I had programmed for other devices from Analog.

In any case, I programmed the device using two different approach. The one suggested by the Datasheet and a simpler one just programming R3, R2, R1 and R0 in sequence.

The first one gave me a carrier on 2.11 GHz for any frequency I try to program. It made me think that this must be the frequency of the VCO, but I am not sure.

Actually when I program different frequency in sequence (like 2036, 1700, 950 MHZ) that carrier does change a little bit (about 10 MHz) for each of the three different settings.

In addition for the 950 MHz case, a lot of spur appeared bellow 800 MHz.

The LD (set to Digital Lock Detection) showed me different values for each case.

The second one showed me those peaks I commented in my previous reply (778, 1556 and 2300 MHz) and the variation for different frequency settings seem to be larger than 10 MHz.

My question is which one is the correct way to program? Why I still cannot lock although I already have noticed that the programming is working?

Before programming in any of the previous case I always had two peaks, one at 1.16 GHz and another one at 2.35 GHz.

Is there any possibility of the device is not working any more? or is there still something missing?

Some tens of minutes ago I was checking the differences between my parameters and the one given my Mini Circuit and I realized that it was using a negative polarity for the VCO! I just changed that and it is perfectly working now!

Then I came here and I saw that you both came up with the same observation! I think I was too focused on the Analog Device datasheet ...